Non-collapsible flexible sealing membrane and seal assembly for rotary shaft equipment

ABSTRACT

A non-collapsible flexible sealing membrane (or bellows) for incorporation in a mechanical seal assembly and use in rotary shaft equipment. The sealing membrane includes a substantially radially outward extending first flange portion, which can be urged into an axially shiftable ring by a biasing mechanism. The sealing membrane further includes a substantially axially outboard extending second coaxial portion, substantially radially inward of the balance diameter of the seal. The horizontal portion is advantageously held fixed to a stub sleeve by an annular band. The angle between the vertical portion and the horizontal portion of sealing membrane enables directional control of the forces acting on stub sleeve and primary ring.

RELATED APPLICATION

The present application is a continuation of U.S. Ser. No. 16/842,004,filed Apr. 7, 2020 which is a continuation of U.S. Ser. No. 15/648,350filed on Jul. 12, 2017 which claims the benefit of U.S. ProvisionalApplication No. 62/361,458 filed Jul. 12, 2016, which is herebyincorporated herein in its entirety by reference.

TECHNICAL FIELD

This invention relates to rotary shaft equipment having mechanical sealassemblies providing a seal between a housing and rotatable shaft of therotary shaft equipment. More particularly, it relates to such rotaryshaft equipment and seal assemblies that include a secondary sealingmembrane such as a bellows.

BACKGROUND

Mechanical seals are used to provide a seal between a rotating shaft anda stationary housing of a pump, compressor, turbine, or other rotatingmachine. End face mechanical seals generally include a primary sealinterface comprising two relatively rotatable seal faces. Frictionalwear between the seal faces can cause a gap to form therebetween,leading to excessive leakage. Accordingly, some end face seals requireregular adjustment in order to maintain the appropriate or axialposition of an axially shiftable seal member (also known as “sealheight”) in order to account for such wear.

Various biasing mechanisms have been contemplated to provide a closingforce to automatically accommodate wear. Such biasing mechanism haveincluded single and multiple coil springs, and metal bellows.

Pusher seal assemblies comprise a dynamic secondary seal (such as ano-ring) to provide a seal between the shaft and the seal membersthemselves. The dynamic secondary seal of pusher seals is generallyconfigured to move axially with the axially shiftable seal member. Thisaxial movement relative to the shaft can cause fretting or shredding ofthe secondary seal due to friction.

Non-pusher seals generally feature a secondary shaft seal that is notintended to move axially relative to the shaft, such as an o-ring(generally used with metallic bellows seals), or an elastomeric bellows,an example of which is provided in FIG. 1 . The depicted mechanical sealcomprises an elastomeric bellows that is driven to rotate with the shaftrelative to the housing. This non-pusher seal can reduce torque stresson the bellows, which are intended to contract and expand to balance theopening and closing forces on the seal faces. At high pressures, such asgauge pressures above about 70 bar(g), however, the shaft itself cantranslate axially. This can create an axial load on the elastomericbellows which can cause the elastomer to rigidly collapse, as shown inthe detail view (where lighter areas are those with higher pressure).This axial rigidity prevents the bellows from effectively counteractingthe closing force provided by the biasing members, leading to excessface pressure, frictional wear, and eventual seal failure.

Ongoing demand for improved productivity, reliability, durability andchanging envelope requirements for pumps and other rotary shaftequipment dictate continued effort for new developments in sealassemblies. In particular, a need exists for mechanical seals that canoperate to seal higher internal pressures. The present disclosurerelates to an advance in seal technology that addresses these needs.

SUMMARY

Embodiments of the present disclosure meet the need for mechanical sealsthat can operate to seal higher internal pressures by providing anon-collapsible flexible sealing membrane (or bellows) for incorporationin a mechanical seal assembly and use in rotary shaft equipment.

The flexible sealing membrane includes a first, substantially radiallyextending portion, which can be urged into an axially shiftable ring byseal components including a plurality of axially spaced springs. Theflexible sealing membrane further includes a second, substantiallyaxially extending portion, substantially radially inward of the balancediameter of the seal, and oriented generally orthogonally to the firstportion. The second portion is advantageously held fixed to a stubsleeve by an annular band. The angle between the first portion and thesecond portion of sealing membrane can provide for directional controlof the forces acting on the stub sleeve. The flexible sealing membranecan reduce the effects on seal performance caused by axial shifting ofthe rotating shaft at high pressures.

In an embodiment, a mechanical seal assembly is adapted for arrangementaround a rotating shaft and comprises an axially shiftable seal ringarranged axially outboard of a axially-fixed seal ring, and a flexiblesealing membrane. The flexible sealing member can include a flangeportion arrangable between the axially shiftable seal ring and a biasingmechanism, the flange portion being axially shiftable relative to therotating shaft by forces transmitted to the flange portion by thebiasing mechanism and the axially shiftable seal ring. The flexiblesealing member can further include a coaxial portion extending axiallyfrom a flexible connection portion at a radially inward extent of theflange portion. The coaxial portion can be held axially fixed relativeto the rotating shaft by an annular band at an outer diameter and anannular stub sleeve at an inner diameter whereby the closing forceapplied to the stationary seal ring by the flange portion remains fixedregardless of the axial position of the flange portion.

In embodiments, the coaxial portion is arrangable at a diameter withinthe balance diameter of the seal and the connecting portion presents athinner cross section than the flange portion and the coaxial portion.

In an embodiment, axially inboard directed forces (such as the inwardtranslation of the rotating shaft) urge the flange portion to shiftaxially inboard and radially inward relative to the coaxial portion andaxially outboard directed forces (such as the outward translation of therotating shaft) urge the flange portion to shift axially outboard andradially outward relative to the coaxial portion.

In an embodiment, the mechanical seal system further comprises ananti-extrusion ring receivable within a groove of the axially shiftableseal ring.

In an embodiment, the stub sleeve is axially fixed to the biasingmechanism by a snap ring.

In an embodiment, the biasing mechanism comprises an axially shiftableannular retainer proximate the flange portion, an annular carrier,axially fixed to a gland plate, and a plurality of radially spacedspring members arranged therebetween.

In an embodiment, a rotating sleeve is operably coupled to the rotatingshaft for rotation therewith and the axially fixed seal ring is operablycoupled to the sleeve by a plurality of pins.

In an embodiment, an annular flexible sealing membrane is adapted forarrangement within a mechanical seal assembly, and comprises a coaxialportion including a radially inboard directed face, an axially outboarddirected face, and a radially outward directed face. The member furthercomprises an axially shiftable flange portion extending radially outwardfrom the coaxial portion and including an axially inboard directed face,a radially outward directed face, and an axially outboard directed face.In an embodiment, the axially outboard directed face of the flangeportion is coupled to the radially outward directed face of the coaxialportion by a flexible connecting portion comprising an axially inboardand radially inward facing facet. The facet can include a first segmentextending axially outboard from the axially inboard directed face of theflange portion and a second segment extending axially outboard andradially inward from the first segment to the radially inboard directedface of the coaxial portion.

In an embodiment, the sealing membrane comprises a flexible elastomer.

The above summary is not intended to describe each illustratedembodiment or every implementation of the subject matter hereof. Thefigures and the detailed description that follow more particularlyexemplify various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter hereof may be more completely understood in considerationof the following detailed description of various embodiments inconnection with the accompanying figures.

FIG. 1 is a cross-sectional view depicting a portion of a seal assemblyand detail of an elastomeric bellows as is known in the art.

FIG. 2 is a cross-sectional view depicting a portion of a seal assemblyaccording to an embodiment.

FIG. 3 is a cross-sectional view depicting a detail of the seal assemblyof FIG. 2 according to an embodiment.

FIG. 4A is a cross-sectional view depicting a portion of a seal assemblyaccording to an embodiment.

FIG. 4B is a cross-sectional view depicting a portion of a seal assemblyaccording to an embodiment.

FIG. 5 is a cross-sectional view depicting a portion of a seal assemblyaccording to an embodiment.

While various embodiments are amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the claimedinventions to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the subject matter as defined bythe claims.

DETAILED DESCRIPTION

FIGS. 2 and 3 are broad and detail (respectively) cross-sectional viewsdepicting a portion of a seal assembly 10 including a flexible,non-collapsible, sealing membrane 100 depicted in conjunction with anarticle of rotary shaft equipment such as a pump, mixer, blender,agitator, compressor, blower, fan, or the like, according to anembodiment of the present disclosure.

As is common for seal assemblies of this type, seal assembly 10 can seala rotating, axially extending, shaft 12 of an article of rotary shaftequipment. Seal assembly 10 can provide a seal for the process chamber14 at the inboard extent of the seal assembly 10 with respect to theambient surroundings 16.

The seal assembly 10 can be arranged coaxial of the shaft 12 in a boredefined by an annular housing 18 coaxial of shaft 12. Various stationary(or non-rotating) components of seal assembly 10 can be operably coupledto housing 18, or a gland plate 20, which is in turn also operablycoupled to housing 18.

Various rotating components can be operably coupled to shaft 12, forrotation therewith. An annular sleeve member 22 is secured to the shaft12 for rotation therewith. An annular flange formation 26 extendsradially outwardly of the sleeve member 22 at the end thereof adjacentthe process chamber 14. A plurality of annularly spaced pins 24 canextend axially through bores in sleeve flange 26.

An axially fixed seal ring 30 (or mating ring) is mounted on the face ofsleeve flange 26 remote from the process chamber 14, for rotationtherewith. Annular o-ring 32 provides a resilient secondary seal betweensleeve member 22 and axially fixed seal ring 30. In embodiments, more orfewer secondary sealing o-rings may be present. Axially fixed seal ring30 includes outboard sealing face 50.

An axially shiftable seal ring 36 (or primary ring) is arranged outboardand adjacent to axially fixed seal ring 30. Axially shiftable seal ring36 includes inboard sealing face 52. Inboard sealing face 52 abutsoutboard sealing face 50.

While, as depicted and described, axially shiftable seal ring 36 isstationary and axially fixed seal ring 30 is rotatable, in embodiments,the relative axial movement can be provided by either the rotating orstationary seal ring.

Inlet 40 can be defined within housing 18 and/or gland plate 20 toprovide a sealing lubricant (not shown) to sealing faces 50 and 52.

Annular bellows, or sealing membrane 100 can present a generallyL-shaped cross-section, comprising a first, generally radially outwardextending, flange portion 102 and a second, generally axially outboardextending, coaxial portion 104. Flange portion 102 and coaxial portion104 can be operably coupled by a flexible connecting portion 106. Aninboard face of flange portion 102 can abut outboard face of axiallyshiftable seal ring 36, creating a pressure tight seal. Coaxial portion104 is substantially or entirely radially inward of the balance diameterof the seal, where the pressure differential across the seal is thegreatest. Flexible connecting portion 106 can present an angular facet108 at a radially inward side and a connecting angle θ between flangeportion 102 and coaxial portion 104 at a radially outward side. Inembodiments, angle θ can be approximately ninety degrees, though otherangles may also be used. Flexible connecting portion 106 can present athinner cross section than flange portion 102 or coaxial portion 104 toenable stretching and compression.

Angular facet 108 can terminate at corner 110 at a radially inwardextent of flexible connecting portion 106. Facet 108 can present anangle 4), relative to the axial axis of between about 100° to about150°. Sealing member 100 is non-collapsible and can comprise a flexiblematerial. Example flexible materials include elastomers such as nitrile,fluroreslastomer, and ethylene propylene rubbers, though other materialscan be used.

Coaxial portion 104 is fixed to an annular stub sleeve 200 by annularband 300. The stub sleeve 200 has a first outer diameter D1, a secondouter diameter D2 and an angled surface 112 connecting the first outerdiameter to the second outer diameter. D2 is greater than D1. Radiallyoutward directed faces (D1, angled surface 112 and D2) of stub sleeve200 can abut coaxial portion 104, facet 108, and axially shiftable sealring 36, respectively. Stub sleeve 200 can present groove 202 to receivesnap ring 204 to locate stub sleeve axially relative to carrier 504(discussed below). In embodiments, stub sleeve 200 can be locatedradially by snap ring 204, hydraulic pressure, or interference fit withcarrier 504 (discussed below) or other components of seal assembly 10.Stub sleeve 200, band 300, and snap ring 204 can comprise steel orstainless steel in embodiments.

Annular anti-extrusion ring 400 can be present in an annular groove ofaxially shiftable seal ring 36 and abut axially shiftable seal ring 36,stub sleeve 200, and sealing member 100. Annular anti-extrusion ring 400can comprise a harder elastomer than sealing membrane 100, such as a 50to 55 (Shore D) durometer carbon filled polytetrafluoroethylene (PTFE).Because extrusion is most likely at the balance diameter of the seal,the inner diameter of anti-extrusion ring 400 can be arranged at thebalance diameter of the seal.

Biasing mechanism 500 can abut flange portion 102. Biasing mechanism 500can comprise an axially shiftable annular retainer 502, axially fixedcarrier 504, and one or more biasing members 506 spanning therebetween.Retainer 502 can be arranged proximate flange portion 102. Retainer 504can present protrusion 508, extending axially inboard outside the outerdiameter of flange portion 102. Protrusion 508 can be radially spacedfrom the outer face of flange portion 102. Carrier 504 can be axiallyand rotationally fixed to gland plate 20 by one or more pins 510, thoughother fixation mechanisms can be used. Biasing members 506 can compriseone or more radially spaced springs, though other biasing mechanismsknown in the art can be used. In embodiments, one or both of retainer502 and carrier 504 can include bores adapted to house at least part ofeach biasing member 506, such that biasing members 506 are partiallylocated within retainer 502 and carrier 504.

Those of ordinary skill in the art will appreciate that the arrangementsdepicted in FIGS. 2 and 3 include components that may be altered oreliminated in other seal assembly embodiments. In addition more or fewercomponents may be incorporated in other embodiments of seal assembliesaccording to the present disclosure.

In operation, rotation of shaft 12 can drive sleeve member 22 andaxially fixed seal ring 30 to rotate relative to axially shiftable sealring 36. Seal lubricant (not shown) can be provided to seal 10 throughone or more inlets provided in housing 18 to lubricate seal sealingfaces 50 and 52 and to create a pressure gradient across sealing faces50 and 52.

The pressure gradient and hydraulic pressure created by the relativerotation of sealing faces 50 and 52 can resulting in an opening force,urging axially shiftable seal ring 36 axially outboard from axiallyfixed seal ring 30. Similarly, a closing force can be provided bybiasing mechanism 500, urging axially shiftable seal ring 36 inboardtoward axially fixed seal ring 30.

Those of ordinary skill in the art will appreciate that the closingforce at a seal face interface can be calculated from the closing area(AC), the opening area (AO), the outer diameter of the stationary ringface (OD), the inner diameter of the stationary ring face (ID) and thebalance diameter (BD), as detailed below:

${{Closing}{Force}} = {{\left( \frac{AC}{AO} \right) \times {Hydraulic}{Pressure}{where}AC} = \frac{{OD}^{2} - {BD}^{2}}{{OD}^{2} - {ID}^{2}}}$

Flange portion 102 can shift axially and radially based on the relativeclosing and opening forces, and the axial translation of the shaftitself, such that the closing force applied to axially shiftable sealring 36 is constant, regardless of the position of flange portion 102.

FIGS. 4A and 4B are detail views of an embodiment of a seal assembly, inwhich some effects of axial movement on sealing membrane 100 can beseen. An axially outward translation of the shaft can be transmitted toflange portion 102 via sleeve 22, axially fixed ring 30, and axiallyshiftable seal ring 36. This movement can cause flange portion 102 tocompress slightly and distort at an angle, preventing any changes in theopening and closing forces at the seal interface. In particular, asdepicted, axially outboard translation of axially shiftable seal ring 36can transmit the opening force to flange portion 102, causing flangeportion 102 to be translated axially outboard and radially outward awayfrom stub sleeve 200 as depicted in FIG. 4A. Conversely, an axiallyinward translation of the shaft can relieve pressure on flange portion102, enabling flange portion 102 to translate axially inboard andradially inward against stub sleeve 200. This contact between sealingmembrane and stub sleeve 200 can further minimize leakage.

A high pressure gradient across sealing faces 50 and 52 can encouragepartial extrusion of flexible sealing membrane 100 between stub sleeve200 and axially shiftable seal ring 36. This can be resisted by theharder material of anti-extrusion ring 400.

Over the life of the seal, sealing faces 50 and 52 will wear relative toeach other. Because sealing membrane 100 can move inboard, towardprocess chamber 14, and outward, away from process chamber 14, over thelife of the seal, it can help to maintain an appropriate seal gap.Hydraulic pressure can keep the axially shiftable seal ring 36 fromcontacting axially fixed seal ring 30 while the flange portion 102 ofsealing membrane 100 moves inboard. The hydraulic pressure can keep theother components, such as stub sleeve 200, in place. Further, becausecoaxial portion 104 is below the balance diameter of the seal, thehydraulic pressure applied to coaxial portion 104 will not affect theclosing force, or the balance diameter itself. Biasing mechanism 500 canbe used to set the working height of the seal and compress flangeportion 102 of sealing membrane 100 against an end of the axiallyshiftable seal ring 36 (distal in relation to the process chamber, andopposite sealing face 52) of the axially shiftable seal ring 36(creating a seal) when no hydraulic pressure is present. Because thevertical force is not altered by the axial movement of sealing membrane100, and the closing force at the interface of sealing faces 50 and 52is not affected.

The maximum axially outboard translation of flange portion 102 andretainer 502 can be defined by a gap provided between an outboard faceof retainer 502 and an inboard face of carrier 504, or by thecompression limit of biasing members 506. In embodiments, translation offlange portion 102 can be limited to prevent bunching, folding over, orother collapsing of sealing member 100 at connecting portion 106. In oneembodiment, translation of flange portion 102 can be limited to maintainangles θ or ϕ.

In addition, because flange portion 102 is held in a radially extendingorientation by axially shiftable seal ring 36 and retainer 502, coaxialportion 104 is held in an axially extending orientation by stub sleeve200 and band 300, sealing member 100 is non-collapsible.

As can be seen in FIG. 5 , the angle θ between flange portion 102 andcoaxial portion 104 of sealing membrane 100 provides for directionalcontrol of the forces acting on stub sleeve 200 and axially shiftableseal ring 36. Coaxial portion 104 allows flexibility of flange portion102 and connecting portion 106 while flange portion 102 is underpressure at the balance diameter of the seal.

Various embodiments of systems, devices, and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the claimed inventions. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, configurations and locations, etc. have been described for usewith disclosed embodiments, others besides those disclosed may beutilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that thesubject matter hereof may comprise fewer features than illustrated inany individual embodiment described above. The embodiments describedherein are not meant to be an exhaustive presentation of the ways inwhich the various features of the subject matter hereof may be combined.Accordingly, the embodiments are not mutually exclusive combinations offeatures; rather, the various embodiments can comprise a combination ofdifferent individual features selected from different individualembodiments, as understood by persons of ordinary skill in the art.Moreover, elements described with respect to one embodiment can beimplemented in other embodiments even when not described in suchembodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims, it is expressly intended thatthe provisions of 35 U.S.C. § 112(f) are not to be invoked unless thespecific terms “means for” or “step for” are recited in a claim.

What is claimed is:
 1. A mechanical seal assembly adapted forarrangement around a rotating shaft, the mechanical seal assembly havinga first and a second seal ring, the first seal ring axially shiftablerelative to the rotating shaft and the second seal ring axially fixedrelative to the rotating shaft, the mechanical seal comprising: a stubsleeve arranged proximate the first seal ring, wherein the first sealring is axially shiftable relative to the stub sleeve in response toaxial movement of second seal ring, the first seal ring having anaxially shiftable seal face that interfaces with an axially fixed sealface of the second seal ring, the stub sleeve including a first outerdiameter, a second outer diameter and an angled surface connecting thefirst outer diameter to the second outer diameter, wherein the secondouter diameter is greater than the first outer diameter; a biasingmechanism that urges the first seal ring toward the second seal ring toengage the axially shiftable seal face to the axially fixed seal facewith a closing force; an annular flexible sealing membrane comprising: aflange portion arranged between the first seal ring and the biasingmechanism, the flange portion being axially shiftable relative stubsleeve; a flexible connection portion positioned within a radiallyinward extent of the flange portion, wherein the flexible connectionportion includes an angular facet that extends from the flexible portionin an axial outward direction; a coaxial portion extending axially fromthe flexible connection portion, the coaxial portion held axially fixedrelative to the stub sleeve; wherein the first outer diameter of thestub sleeve abuts the coaxial portion, the angled surface abuts theangular facet of the flexible connection portion, and the second outerdiameter of the stub sleeve abuts the first seal ring.
 2. The mechanicalseal assembly of claim 1, wherein the angular facet that extends fromthe flexible portion in the axial outward direction forms an angle ϕwith the coaxial portion, wherein the angle ϕ is between 100° and 150°.3. The mechanical seal assembly of claim 1, wherein axial translation ofthe first ring relative to the biasing mechanism urges the flangeportion to shift axially inboard and radially inward relative to thecoaxial portion.
 4. The mechanical seal assembly of claim 1, whereinaxial translation of the first ring relative to the biasing mechanismurges the flange portion to shift axially outboard and radially outwardrelative to the coaxial portion.
 5. The mechanical seal assembly ofclaim 1, wherein the connecting portion presents a thinner cross sectionthan the flange portion and the coaxial portion.
 6. The mechanical sealassembly of claim 1, further comprising an anti-extrusion ringreceivable within a groove of the axially shiftable first seal ring. 7.The mechanical seal assembly of claim 1, wherein the stub sleeve isaxially fixed to the biasing mechanism by a snap ring.
 8. The mechanicalseal assembly of claim 1, wherein the biasing mechanism comprises anaxially shiftable annular retainer proximate the flange portion, anannular carrier, axially fixed to a gland plate, and a plurality ofradially spaced spring members arranged between the carrier and theretainer.
 9. The mechanical seal assembly of claim 1, further comprisinga rotating sleeve operably couplable to the rotating shaft for rotationtherewith and wherein the axially fixed second seal ring is operablycoupled to the sleeve by a plurality of pins.
 10. The mechanical sealassembly of claim 6, wherein the sealing membrane comprises a flexibleelastomer.
 11. The mechanical seal assembly of claim 10, wherein theanti-extrusion ring comprises an material of a greater hardness than theflexible elastomer of the sealing membrane.
 12. The mechanical sealassembly of claim 1, wherein the closing force applied to the axiallyshiftable first seal ring by the flange portion is not altered by theaxial position of the flange portion relative to the rotating shaft.